Three visits, two modalities, and one ankle… Go!

Posted May 30, 2018

This 64-year-old female fell approximately three weeks ago, and presents with right ankle pain.

Prior to this incident, this patient’s foot was assessed in 2015 and 2017. Images 1 and 2 are radiographs of the patient’s foot from 2015. Images 3 and 4 are radiographs of the patient’s foot from 2017. Images 5 and 6 are MRIs of the patients foot from the current visit (2018).

Q1 – From images 1 through 6, what do you think the most likely diagnosis would be?

X-ray (2015)

X-ray (2015)

X-ray (2017)

X-ray (2017)

MRI (2018) Sagittal STIR

MRI (2018) Sagittal STIR

A1 – The most likely diagnosis is a full-thickness tear of the peroneus longus tendon. The diagnosis can be made using plain film radiographs. The os peroneum, noted on the 2015 and 2017 exams (images 7 through 10, green arrows), is fractured and distracted on the 2017 study (images 9 and 10, blue arrows).

*Given how uncommon fractures of the os peroneum are, they may be mistaken for bipartite or multipartite sesamoids. Typically, association of such fractures are with either acute or chronic peroneal longus tendon dysfunctions where:

Acute – Result from peroneal longus tendon rupture upon injury

Chronic – Degeneration / Tearing resulting from friction of fragments along the tendon

With distal peroneus longus ruptures, displacement and proximal migration of an intact os peroneum can be seen.